The 19-year-old joined the Potters on deadline day and will be loaned back to the Championship side for the remainder of the season.
Clark expects Butland to reach the very top in his career and praised the youngster for snubbing a move to Chelsea in the January transfer window.
"We've lost in terms of the long term, in my opinion, the best goalkeeper in Europe," Clark told BBC West Midlands. "We've got him back for the rest of the season, but I would just love a bit more time to work with him.
"I think many young players would have jumped at [Chelsea] for the profile and financial rewards. But Jack looks at the bigger picture. He's not only a top player but he's a top young guy.
"He knows eventually he's going to be at a top club, and that's not disrespectful to Stoke who are a great Premier League club and have a fantastic manager, but ultimately he's going to end up at a Champions League club competing for the higher honours."
Butland will officially move to the Britannia Stadium in the summer.